Teach cloud formation when there's not a cloud in the sky! This apparatus duplicates atmospheric conditions during cloud formation. It consists of a special glass flask with a rubber hose connection, pinch clamp, and large, thick walled, rubber bulb. When the atmospheric pressure is lowered, smoke particles are introduced into the chamber and a nucleus for the formation of water droplets is produced. By compressing and suddenly releasing the bulb, a dense cloud forms in the flask.